Many processes and devices have been implemented and used for measuring more than one measurand simultaneously. A miniature MEMS (Micro-Electro-Mechanical Systems) based flow or pressure transducer can be used to measure flow or pressure and with a reliable accuracy. Such MEMS based sensors have been implemented, for example, in various independent sensing devices, such as medical applications, some of which utilize silicon based thermal mass flow or piezoresistive sensing technology for measuring wide ranges of flow and pressure. Other multiple sensing implementations, for example, include instrumentation and environmental applications.
MEMS involve the integration of micro-mechanical elements, sensor actuators, and electronic components on a common silicon substrate through the use of micro fabrication technology. While the electronics can be fabricated using integrated circuit (IC) process sequences (e.g., CMOS, Bipolar, or BICMOS processes), the micromechanical components can be fabricated utilizing compatible “micromachining” processes that selectively etch away parts of the silicon wafer or add new structural layers to form the mechanical and electromechanical devices.
The majority of prior art transducers are either sold with calibrated or un-calibrated analog outputs or as transducers with small-signal outputs, either of which may need to be conditioned and calibrated by the end user within their system. Further, the analog signals conditioned by the user must pass through an analog-to-digital converter so that the output signals can be processed by the system, which may be microcontroller-based. The most common measurands are flow, pressure, temperature and humidity and the output signals from the raw transducers are typically not linear and vary as a function of temperature.
In some sensing applications, it is preferred that signal conditioning/signal amplification capability be incorporated into the sensor. It is believed that there are currently no sensors available for efficiently and accurately measuring multiple measurands. Therefore, to overcome the foregoing shortcomings, it is desirable to provide a suitable packaging method and/or system for measuring multiple measurands. It is further believed that if such a sensor is implemented, the resultant sensor design can assist in lowering installation and development costs, while eliminating secondary operations and shortening the design cycle time.